This application is a continuation of International application Serial No. PCT/US2011/024907 (International Publication No. WO/2011/100746), having an international filing date of Feb. 15, 2011. This PCT application claims priority to and claims benefit from U.S. provisional patent application Ser. No. 61/304,713, filed on Feb. 15, 2010. The entire specifications of the PCT and provisional applications referred to above are hereby incorporated by reference.
The presently described technology relates generally to a method for producing esteramines through transesterification or esterification processing between alkanolamines and alkyl esters or fatty acids. More specifically, the present technology provides methods for decreasing the reaction time and/or lowering the reaction temperature needed to react alkanolamines and fatty acid alkyl esters, fatty acids, or mixtures thereof through utilization of zinc catalysts.
Esterification reactions of alkanolamines with carboxylic acids or fatty acids have traditionally been catalyzed with an acid catalyst, such as, for example, phosphorous acid, sulfuric acid, or the starting carboxylic acid itself. Such acid catalysts have several drawbacks, including a very slow reaction time.
Sodium or potassium alkoxides (e.g., methoxides), in general, are also used with alkyl esters for transesterification reaction processing. Such processes are seriously inhibited, however, by moisture and/or acidic impurities. These types of alkoxides also produce resultant transesterified products that, in many instances, exhibit the viscosity of a gel, due to side reactions. Potassium hydroxide is often used to catalyze the reaction between triglycerides and triethanolamine. However, the reaction is still very slow and is believed by those skilled in the art to be due, in part, to the potassium hydroxide immediately reacting with acidic impurities during reaction processing to generate water and other potassium salts, which may, or may not, be of any use as catalysts.
Titanium catalysts, sold commercially under the brand name TYZOR® have also been used to catalyze the reaction of triethanolamine and fatty acid. Such titanium catalysts, however, also have several drawbacks. In particular, titanium catalysts tend to form titanium precipitates in solution. Residual titanium catalysts can also interfere with product stability and result in a poorly colored product that may require further bleaching. In addition, when titanium catalysts are used with triethanolamine and fatty acid, the resulting ratios of monester, diester and triester esteramines are not in line with established product specifications. Further, it is known that the activity of titanium catalysts are negatively impacted by amines in the absence of carboxylic acids. This affect, is a hindrance when a carboxylic acid feed is replaced by an alkyl ester feed such as methylester, in conducting the reaction to produce the esteramine.
In view of the above drawbacks, there is a need for an improved catalyst that can decrease the esterification or transesterification reaction time for the reaction between alkanolamines and carboxylic acids or fatty acids, or alkyl esters. There is also a need for a catalyst that can produce an esteramine product that is storage stable, has a good color, and has ratios of monoester, diester and triester esteramines that meet existing product specifications for esteramines.